Photovoltaic cells or solar panels directly convert sunlight into electric energy. The efficiency of photovoltaic cells is increasing with improvements in cell conversion efficiency, currently approximately 15% for commercially available multi-crystal silicon cells. With these increased efficiencies and a reduction in cell manufacturing costs, photovoltaic cells or solar panels are becoming an important and viable source of electric power. However, even with these increasing efficiencies and reducing costs, photovoltaic cells or solar panels only have limited use because they can produce electrical power for only a few daylight hours. Therefore, there is a need to extend the use of photovoltaic cells or solar panels, making them efficient producers of electrical energy independent of sunlight or inclement weather. There is additionally a need to supply continuous or on demand electrical power, independent of available daylight or the weather.